Molecular detection of spotted fever group Rickettsia in Dermacentor silvarum from a forest area of northeastern China.

In total, 676 Dermacentor silvarum Olenev (Acari: Ixodidae) from a forest area of Jilin Province in northeastern China were examined by polymerase chain reaction for the presence of spotted fever group (SFG) Rickettsia. The overall positive rate was 10.7%, with a 95% confidence interval from 8.3 to 13.0%. The SFG Rickettsia infection was more prevalent in adults than in nymphs, and in fed ticks obtained from domestic animals than in those collected on vegetation. Sequence analysis of the partial outer membrane protein A gene confirmed the existence of R. sibirica and discovered a novel rickettsial agent in this area, the sequence of which was identical to that of DnS14 genotype Rickettsia previously reported in the former Soviet Union.